One aspect of rail vehicle safety is ensuring that the rail vehicles, such as trains, do not exceed maximum allowable speeds. Maximum speed limits may be dictated for the rail vehicle throughout an entire rail system. Some sections of track may have different maximum speed limits than others. Furthermore, slow orders, which comprise temporary speed restrictions, may be issued for an entire rail system (e.g., a lower speed on hot days due to a danger of track buckling) or a portion of the rail system (e.g., due to workmen near a particular section of track).
To reduce fuel consumption and emissions, some trains and other powered systems may use an on-board energy management system, fuel saving system, speed control system, or other train control system. On-board energy management systems, for example, may incorporate (or otherwise utilize) information about the rail vehicle and the route to provide a speed profile. The speed profile determines the speed that the train will travel throughout the trip and ensures that the speed of the train does not exceed any maximum speed limits for the route. Based on the speed profile, braking curves may be generated for portions of a trip during which a speed reduction is needed. The train is controlled according to the speed profile, either automatically or by the on-board energy management system suggesting the control settings to the operator of the train. The maximum speed limits issued for a particular section of track are normally adhered to whether the speed is manually controlled or controlled via an automated system.
Typically, speed profiles are generated for a train based on a worst case scenario. A braking curve, which may be generated based on the speed profile, determines the degree to which the braking system of the train is applied to achieve a desired speed reduction. Because sometimes a train may be traveling in the rain (in which case the track will be wet) and/or with a tail wind, the braking curves are generated under the assumption that the train is braking on wet tracks with a tail wind. When such a braking curve is employed during dry conditions and with no wind (or when the train is traveling into a head wind), the train may begin braking earlier (and for a longer duration) than needed to achieve the required speed reduction. As a result, the duration of the train trip may be longer than necessary and longer than if the braking curves were generated for the existing conditions (e.g., dry, no wind). If the duration of the train trips over a particular route can be shortened, more trains can be permitted to use the tracks of the route over a given time period. In addition, unnecessary braking also may result in unnecessary fuel consumption.
Likewise, slow orders may sometimes be generated based on environmental conditions that no longer exist or do not exist at the location of the train. As a result, a train may travel at a slower speed than necessary, which also may result in fuel waste and increase the duration of the trip.
Consequently, there is need for a system and method for determining and controlling the speed of a rail vehicle consist based, at least in part, on environmental information. These and other features may be provided by some embodiments of the present invention.